Method and apparatus for clarifying a liquid



Feb. 24, 1970 K. s. ARvANrrAKls 3,497,452

METHOD AND APPARATUS FOR CLARIFYING A LIQUID 14 Shets-Sheet vl Filed sept. 9, 196s Fel 24 1970 K. s. ARVANITAKIS 3,497,452

METHOD ANDAPPARATUS FOR CLARIFYING A LIQUID Filed Sept. 9d 1968 14 Sheets-Sheet 2 Feb. 24, 1970 K. sARvANlTAKls METHOD ANDPPARATUS FOR CLARIFYING A LIQUID 6 n 5 H e n h S m f n :f H w v l l l 4/l me 3 so o a M s l M o @mx 0 6H. a y Y 2 o m 1 2 n. M Ou 2 M. m m4 n E F IMI".

.SEQD FILTER Feb. 24, 1970 K.s.ARvANi1-A| |s y 3,497,452

METHOD AND APPARATUS FOR CLARIFYING A LIQUID med sept. 9, 1968 4,8 y14 sheets-sheet 4 h @ff l i l 34o 3/3 3/4 'f o l G 0452 I 4,24 r 4 I G. V, 3/6 f 43o| 428 I 364 32o# o I o 426'" I 352 G O o!! o 0 1| 0 Feb. 24, 1970 Filed sept. e. 196K K. S. ARVANITAKIS METHOD AND APPVARATUS FOR CLARIFYING A LIQUID 14 Sheets-Sheet 5 Feb 24, 19.70 K. s. ARvANrrAKls 3,497,452

METHOD AND APPARATUS FOR CLARIFYING A LIQUID Filed sept. 9, 11968 14 Sheets-Sheet 6 'I 45g 3/8 466" l 460 l] n l' 400 396 II f ,462 3 46 WATER 'I 2: i '353 D 398,. d f son. ENT I I y 354 j?, /7 u I l Fell 24, 1970 K. s. ARVANITAKIS. l 3,497,452

METHOD AND APPARATUS FOR CLARIFYING A LIQUID Filed Sept. 9, 1968 v 14 Sheets-Sheet 7 Feb- 24 1970 K. s. ARvANiTAKls 3,497,452

METHOD AND APPARATUS FOR CLARIFYING A LIQUID 608 as mFz/amlw A 6/0 @1 ,gf

Feb. 24, 1970 f K.`s. ARVANITAKIS 3,497,452

METHOD ANDPRA'I'US FOR CLARIFYING A LIQUID Filed Sept. 9, 1968 s 14 Sheets-Sheet 9 Feb- 24, 1970 K. s. ARvANrrAKls 3,497,452

METHOD AND APPARATUS FOR CLARIFYING A LIQUID Filed Sept. 9, 1968 14 Sheets-Sheet 10 METHOD ANDAAPPARATUS FOR CLARIFYING A LIQUID Filed sept. s. 196e Feb. 24, 1979 K. s. ARvANlTAKls 14 Sheets-Sheet 11 Feb. 24, 1970 K. s. ARvANlTAKIs 3,497,452

l METHOD ANDAPPARATUS FOR CLARIFYING A LIQUID Filed sept. 9. 196e 14 sheets-sheet 1a Feb. 24, 1970 K'. s. ARVANITAKIS 3,4975452 METHOD AND,APPARATUS FOR CLARIFYING A LIQUID 14 lSheng-sheet 1s `F-.c

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nited States Patent Office 3,497,452 Patented Feb. 24, 1970 US. Cl. 210--39 57 Claims ABSTRACT OF THE DlSCLOSURE A method and apparatus for clarifying a liquid with a filter and for intermittently removing filter cake deposited on the surface of the filter automatically. The principal filtering operation is accomplished by pumping an unclarified liquid from a source through a primary filter, and then conveying the liquid clarified thereby to a receptacle, thus leaving an accumulation of filter cake on the surface of the filter. The automatic cleaning operation is accomplished by temporarily interrupting the filtering operation, dislodging the filter cake from the filter surface into unclarified liquid adjacent to the filter surface by means of a wiper m-oving at less than 1000 inches per minute relative to the surface of the filter, and removing dislodged filter cake from the unclarified liquid by recirculating the liquid within the filter apparatus through a secondary filter until the filter cake is deposited on the secondary filter.

CROSSREFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of the following co-pending applications by the same applicant, now all abandoned:

Method and Device for Cleaning Dry Cleaning Solvent, Ser. No. 459,588, filed May 28, 1965.

Apparatus and Method for Clarifying a Dry Cleaning Solvent, Ser. No. 582,887, filed Sept. 29, 1966.

Apparatus and Method for Clarifying a Dry Cleaning Solvent, Ser. No. 652,336, filed July l0, 1967.

Apparatus and Method for Clarifying a Liquid, Ser. No. 664,536, filed Aug. 30, 1967.

Apparatus and Method for Clarifying a Dry Cleaning Solvent, Ser. No. 664,480, filed Aug. 30, 1967.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to an improved method and apparatus for clarifying liquids with a filter, wherein filter cake deposited on the filter is intermittently dislodged from the filter and removed from the system automatically.

Description of the prior art Many industrial operations utilize filter apparatus for clarifying liquids. In a dry cleaning operation, for example, an expensive solvent (e.g., perchloroethylene) is used in order to remove solid particles, such as lint and dirt, and chemical contaminants, such as higher fatty acids, from soiled clothing. Since this solvent is expensive, industrial dry cleaning operations utilize filter apparatus in conjunction with a dry cleaning machine for removing the solid and chemical impurities from the dry cleaning solvent so that the solvent may be re-used.

In order to remove both solid and chemical impurities from the solvent, one of two types of filter apparatus is generally used. One type of filter apparatus provides a mechanical filter for removing solid particles (e.g., a fine mesh screen through which the liquid fiows) in series with a chemical filter for removing chemical impurities (e.g., a filter composed of activated charcoal, diatomite, or some other material that is capable of adsorbing chemical impurities from the solvent). Another type of filter provides not only a mechanical filter but also provides a device for adding an adsorptive powder to the unclarified solvent before the liquid passes through the mechanical filter. As the solvent passes through the mechanical filter from the high-pressure side to the lowpressure side, the adsorptive material as well as the solid impurities form a filter cake deposit on the high-pressure side of the filter, thus creating a layer of adsorptive material on the surface of the filter. Thereafter, when unclarified liquid passes through the mechanical filter, it also undergoes chemical filtration as it passes through the layer of adsorptive material.

In a typical dry cleaning operation, a dry cleaning machine and filter apparatus are used cyclically. When a load of clothing is being washed, solvent is circulated continuously from the dry cleaning machine to the filter apparatus and then back to the dry cleaning machine, and the returned solvent is supposed to be free of solid and chemical impurities, so that it may be reused to remove additional solid yand chemical impurities from the load of soiled clothing in process. When the clothes are clean, the dry cleaning machine and the circulation of solvent through the filter apparatus are stopped, and the dry cleaning machine is reloaded with another load of dirty wash.

One of the principal problems encountered in a dry cleaning operation (as well as in all other filtering operations in which a substantial quantity of filter cake is removed from a liquid) is that solid impurities and adsorptive materials removed from the liquid accumulate on the surface of the filter and clog the lter, thereby impairing the efficiency of the filter apparatus. Therefore, many attempts have been made to devise methods and apparatus for removing filter cake from a filter surface and from a filter apparatus. Unfortunately, until now, these attempts have not been successful in producing a filter that can be cleaned frequently without costly and time-consuming delays in the filtering operating and without injury to the filter.

One type of filter apparatus previously developed utilizes a replaceable filter. When this filter becomes clogged, the operator discontinues the filtering operation, disassembles the filter apparatus, and replaces the filter with a new one. This procedure, of course, requires a great deal of time and much effort, so this apparatus is not readily adaptable to an operation in which the filter requires frequent cleaning.

Several filters have been developed in which filter cake may be dislodged from a filter surface without disassembling the filter apparatus. Some of these employ filter cleaning means such as brushes, Scrapers, or sprayers that operate on the filter cake from the high-pressure or upstream side of the filter, While others employ a backwashing action (i.e., reversing the fiow of liquid through the filter) that operates on the filter cake from the lowpres sure or downstream side of the filter.

A primary problem that has characterized wiping approaches in the prior art involves the possibility that the use of a rigid scraper to wipe filter cake from a delicate filter surface, often a fine mesh screen, might damage or puncture the screen. Another problem is that an improper wiping speed can cause a wiping member to force a filter cake into and through the fine mesh screen and into the clarified liquid on the low-pressure side of the filter (thereby clogging the filter and contaminating the clari- 3 fied liquid), and it can cause the remaining filter cake to break into particles that are so finely divided that the settling of the dislodged particles from the liquid occurs very slowly, if at all.

One type of prior art device employing a means for dislodging filter cake from a filter surface without disassembling the filter apparatus is a dual-chamber filter specifically designed for clarifying a dry cleaning solvent. In the operation of this apparatus, unclarified liquid from a dry cleaning machine is pumped to a primary filter chamber, through a primary filter mounted in the chamber, and then back to the dry cleaning machine, leaving a filter cake deposit on the primary filter. When the accumulation of filter cake on the primary filter impairs the passage of liquid through the filter, a mechanical scraping device dislodges the filter cake from the filter and permits it to settle to .the bottom of the chamber. When the accumulation of filter cake on the bottom of the chamber reaches an undesirable level, the filtering operation is interrupted and the entire contents of the primary filter chamber (including the filter cake) are pumped to a secondary or sludge filter chamber, wherein the liquid is removed from the lter cake by a secondary or sludge filter and is returned to the dry cleaning machine for re-use.

There are several disadvantages in this type of apparatus. First of all, when the filter cake is dislodged from the primary filter, much of it remains in suspension in the surrounding solvent, so the operator must wait until the force of gravity causes the particles to settle to the bottom of the chamber, before resuming the filtering operation in order to prevent the filter cake from being re-deposited on the primary filter. This waiting period results in a long delay in the filtering operation.

Another disadvantage in this filtering system is that the entire primary filter chamber must be evacuated in order to remove the sludge from the bottom of the chamber, thus requiring that the chamber be completely refilled every time the filter cake is removed before filtering can resume. Refilling the primary filter chamber creates additional delay in resuming the dry cleaning operation, and thus makes it impractical to evacuate the chamber after every dry cleaning cycle.

Still another disadvantage with this prior art system is that evacuation of the chamber leaves deposits of filter cake (like a bathtub ring) on the filter and on the walls of the primary filter chamber as the liquid is drained from the chamber, so the removal of filter cake from the primary filter chamber is incomplete.

Another example of a filter apparatus heretofore known comprises a primary filter and a secondary filter mounted in the same filter chamber. In the normal operation of this device (which is also specifically designed for filtering dry cleaning solvents), used dry cleaning solvent is pumped from a dry cleaning machine, through the primary filter, and then back to the dry cleaning machine, thereby depositing a filter cake on the primary filter. The secondary filter, mounted at the bottom of the filter chamber, is inoperative during the normal dry cleaning cycle. The primary filter is cleaned by backwashing the filter (i.e., reversing the flow of the solvent through the lter) and, at the same time, actuating the secondary filter at the bottom of the tank. This causes the filter cake to break away from the primary filter and drift to the bottom of the tank. The secondary filter returns solvent directly back to the dry cleaning machine for re-use.

The principal disadvantage of this type of apparatus is that the primary filter must be cleaned by backwashing in order to create the fiow of liquid and dislodged filter cake from the primary filter to the secondary filter, and backwashing is very hard on a filter and reduces itslife considerably. Most types of filters are constructed of a fine mesh screen supported only on the low-pressure side by a support structure, and this fine mesh screen distends and disrupts easily like a balloon when subjected to pressure from its low-pressure side. Therefore, backwashing is not feasible with most types of lters.

Another disadvantage in the above-described device is that liquid passing through the secondary filter returns directly to the dry cleaning machine, so it must be pumped all the way back to the filter for backwashing. Consequently, it takes a long time for the liquid to fiow from the secondary filter to the primary filter, and this may prolong the cleaning operation. Moreover, the dry cleaning machine must be operative during the filter cleaning operation in order to pump liquid back to the filter apparatus for backwashing, even though it is normally stopped at the end of the dry cleaning cycle. If this cleaning operation were to be performed regularly (once per cycle, for example), the dry cleaning machine would be pumping liquid continuously, and this would result in greater fatigue and greater wear on the dry cleaning machine than would result from a normal cyclicaloperation.

Still another disadvantage in this filter apparatus is that the apparatus is constructed so that the secondary filter is operative only during a cleaning cycle. During the normal filtering operation, the secondary filter is deactivated, so gravity is the only force operative on the suspended particles to cause them to settle from the liquid in the filter chamber. This natural settling operation occurs quite slowly, so most of these particles are removed from the liquid by the primary filter, thus resulting in a rapid accumulation of filter cake on the surface of the primary filter. Therefore, frequent cleaning and frequent and harmful backwashing of the filter is required.

Another disadvantage in both of the filter systems dcscribed above is that filter cake is removed from the primary filters only when the filter cake begins to clog the filter, and the systems are not designed for frequent cleaning. Consequently, the openings in the primary filter for the passage of liquid must be quite large in order to avoid frequent clogging of the filter. This, of course, reduces theeffectiveness of the filtering operation.

SUMMARY OF THE INVENTION Since the utilization of the prior art filtering devices described above involves either an incomplete and timeconsuming cleaning process or entails the harmful backwashing of the filter, neither of these devices are completely satisfactory for use in a large scale industrial process, such as in the dry cleaning industry, where almost continuous operation of a filter apparatus working at peak efiiciency is required. The present invention obviates these deficiencies of the prior art devices and provides several embodiments of filtering apparatus that are capable of functioning in a cyclical operation at peak efiiciency at all times.

Briefly, in the normal filtering operation of the several embodiments of the subject invention described below, unclarified liquid pumped from a source, such as a dry cleaning machine, enters a filter chamber in the filter apparatus, flows through a primary filter mounted therein, and fiows out of the filter chamber to a receptacle (e. back to the dry cleaning machine), leaving a filtrate posit on the surface of the primary filter.

In several embodiments of the invention, a portion of the liquid is filtered by a secondary filter, which is disposed either in an auxiliary filter chamber or in the same filter chamber below the primary filter. The latter approach is especially preferred because the secondary filtering action that is achieved creates a slight downward fiow of liquid within the chamber and enhances the settling of solid particles from the unclarified liquid.

Another modification shown in several embodiments of the subject invention is the use of a turbulence suppressor at the inlet of the primary filter chamber in order to ensure that the liquid in the chamber remains in a quiescent state. One embodiment includes a turbulence suppressor that also functions as a wiper for removing accumulated filter cake from the primary filter.

5, intermittently, the normal filtering operation is interrupted for a short time while the filter cleans itself. The

flow of liquid through the primary filter is stopped, and v a wiper mounted in the primary filter chamber in contact with the primary filter wipes accumulated filter cake from the high-pressure side of the primary filter and dislodges it into unclarified liquid surrounding the primary filter in'the primary filter chamber. In one embodiment, a sprayer is also used to assist the wiper in dislodging the filter cake.

For the most effective wiping action, the preferred approach of the subject invention teaches that the relative motion between the wiper and the high-pressure side of the primary filter should be less than about 1000 inches per minute, and, ideally, about 200 to about 400 inches per minute. This prevents the filter cake from being forced through the filter by the wiper and causes the filter cake to break-off in large chunks that settle rapidly.

In order to ensure that the dislodged filter cake is not re-deposited on the filter surface when the filtering operation is resumed, the unclarified liquid entraining the dislodged filter cake is recirculated within the filter apparatus through a secondary lter located either at the bottom of the primary filter chamber or in separate filter chamber. This action transfers the suspended filter cake to the secondary filter and returns clarified liquid to the area surrounding the high-pressure side of the primary filter. When the secondary filter is mounted at the bottom of the primary filter chamber, the transfer of filter cake to the secondary filter is enhanced by the natural settling action attributable to the force of gravity.

There are several -advantages to the important recirculation feature of the subject invention. First of all, the transfer of filter cake from the vicinity of the primary filter to the secondary filter is much more rapid and more thorough than can be accomplished by merely allowing the filter cake to settle under the influence of gravity or by draining the tank. Recirculation produces a fiushing action that is much more vigorous than the settling or draining processes employed in the prior art filters.

Another advantage to the recirculation approach is that the filter cake is transferred to the secondary filter while the filter chamber remains full of liquid, so the primary filter is ready to commence another filtering operation immediately after the filter cake is transferred to the secondary filter. As stated above, additional time to refill the filter chamber is required when the inefficient draining process is used.

Still another advantage of the recirculation approach of the instant invention is that the primary filter is cleaned and the filter cake is transferred to the secondary filter without requiring any harmful backwashing of the primary filter, as is required in certain prior -art filters.

Still another advantage of the instant invention is that this flushing or recirculating of liquid within the filter chamber is accomplished independently of the source from which the unclarified liquid is obtained. Thus, in an industrial use, such -as in a dry cleaning operation, the dry cleaning machine need operate only during the washing cycle. During reloading, the dry cleaning machine may be completely inactive while the filter apparatus cleans itself independently and automatically.

After the filter cake suspended in the unclarified liquid has been transferred to the secondary filter, the recirculating means is automatically deactivated, and the filter is ready to resume another cycle with a freshly cleaned primary filter.

An additional feature disclosed in connection with one of the embodiments of the subject invention described below is an automatic cleaning device for the secondary lter. After the filter cake has been dislodged from the high-pressure side of the primary filter and transferred to the high-pressure side of the secondary filter by recirculating the liquid within the filter apparatus (i.e., recirculating the liquid from the primary filter chamber to the secondary filter chamber, through the secondary filter, and back to the primary filter chamber), and after the normal filtering operation has resumed, a wiper mounted in the secondary filter chamber wipes the filter cake from the high-pressure side of the secondary filter and dislodges it into the liquid surrounding the secondary filter. This filter cake then settles from the liquid into a removable basket at the bottom of the secondary filter chamber, leaving the secondary filter clean for the next filter cleaning operation.

It will be recognized readily that the methods and apparatus for filtering liquid described herein are applicable to a variety of filtering operations and are especially applicable to a dry cleaning operation because the filter is able to operate in successive continuous cycles at peak efficiency. At the completion of a washing cycle of a dry cleaning machine, the filter will clean itself automatically while the operator is removing the cleaned wash and inserting another load of dirty Wash into the dry cleaning machine. By the time the dry cleaning machine is ready to resume operation, the filtering apparatus is cleaned and ready to reclarify the dry cleaning solvent.

Since this apparatus permits frequent removal of filter cake from the primary filter, clogging of the primary filter will be less of a problem than in the prior art filters, so that smaller openings in the primary filter (i.e., a filter screen with a finer mesh) may be employed.

Accordingly, it is a primary object of this invention to provide methods and apparatus for clarifying a liquid that facilitate frequent cleaning of the filter without any action on the part of the operator and with a minimum of interruption in the filtering process.

Another object of the invention is to provide an effective wiper for thoroughly dislodging filter cake from a filter in a filter apparatus without damaging the filter.

Another object of this invention is to provide a wiper as described above that also functions as a turbulence suppressor to ensure that liquids entering the filter apparatus are in a quiescent state.

Still another object of this invention is to provide an effective speed for wiping filter cake from the surface of a filter in a filter chamber such that filter cake is not forced through the filter by the wiping action and filter cake is not broken into finely divided particles that are slow to settle away from the filter in the filter chamber.

A further object of this invention is to provide methods and apparatus for actively transferring filter cake from a primary filter mounted in a filter chamber to a secondary filter without draining the filter chamber and without backwashing the primary filter.

Another important object of this invention is to provide methods and apparatus for transferring filter cake entrained in a liquid surrounding a primary filter in a filter apparatus to a secondary filter in the filter apparatus by recirculating the liquid within the filter apparatus through the secondary filter, without any backwashing of the primary filter.

Still another object of this invention is to provide methods and apparatus for recirculating liquid within a filter apparatus as described above wherein the liquid ows from the high-pressure side of the primary filter through the secondary filter and returns to the high-pressure side of the primary filter through directing means (such as sprayers or nozzles) that direct the returning liquid against the filter cake on the primary filter and help the wiper to dislodge the filter cake from the primary filter.

A further object of this invention is to provide methods and apparatus for clarifying a liquid wherein, during normal filtering operation, most of the liquid is clarified by a primary filter mounted in the filter apparatus, but a small portion of the liquid is filtered by a secondary filter mounted below the primary filter in the filter apparatus, so that the settling of solid particles suspended in the iquid will be aided by the downward fiow of liquid withn the filter apparatus.

Another object of this invention is to provide a device For cleaning the secondary filter described above without iisassembling the filter apparatus.

Still another object of this invention is to provide a ilter apparatus having primary and secondary filters which are mounted in separate, communicating filter zharnbers, wherein the secondary filter chamber may be solated from the primary filter chamber and disassembled ind the filter cake removed therefrom without draining ;he primary filter chamber and without disrupting the ltering operation of the primary filter.

These and other objects, advantages, and features of :he subject invention Will hereinafter appear, and, for purposes of illustration but not of limitation, several exzmplary embodiments of the subject invention are described below and illustrated in the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a perspective view of one embodiment of the subject invention, with clean-out doors removed in order to show the interior construction of the device;

FIGURE 2 is a perspective view of the embodiment shown in FIGURE l, showing the opposite side of the device;

FIGURE 3 is a cross-sectional view, taken along line 3 3 of FIGURE 1;

FIGURE 4 is a cross-sectional end view of the ernbodiment shown in FIGURE 1, taken along line 4 4 of FIGURE 3;

FIGURE 5 is a cross-sectional view, taken along line 5 5 of FIGURE 1, showing the construction of a chemical filter and a chamber for the chemical filter;

FIGURE 6 is a cross-sectional view of a portion of a mechanical filter shown in FIGURES 3 and 4, taken along line 6 6 of FIGURE 4, showing the relation of spray nozzIe relative to screen disc components of the filter;

FIGURE 7 is a cross-sectional view, taken along line 7 7 of FIGURE 6, showing an end cross-sectional view of a mechanical filter element and a spray nozzle and header adjacent to the filter element;

FIGURE 8 is a perspective view with a portion broken away of one of the mechanical filter elements shown in FIGURE 6, showing the interior construction of the element;

FIGURE 9 is a cross-sectional view taken on line 9 9 of FIGURE 7 showing the construction of a wiper;

FIGURE 10 is a schematic timing chart for the embodiment shown in FIGURE l;

FIGURE l1 is a side elevational view of a portion of a second embodiment of the subject invention, shown for exemplary purposes connected to a conventional dry cleaning machine;

FIGURE 12 is a cross-sectional view of several filter elements in a primary filter mounted within the filter apparatus shown in FIGURE l1;

FIGURE 13 is a cross-sectional end View of the filter elements shown in FIGURE 12;

FIGURE 14 is a perspective view of a portion of the embodiment shown in FIGURE 11 with a portion of the filter apparatus broken away to Show the filter elements in FIGURES 12 and 13 as they are mounted in the tank, and to show the interior construction of the filter apparatus;

FIGURE l5 is a detailed fragmentary View of a portion of a turbulence suppressor shown in FIGURE 14;

FIGURE 16 is a perspective view of the embodiment shown in FIGURE 11, with portions broken away to show the construction of a separator and a lower portion of a tank shown in FIGURE 14;

FIGURE 17 is a perspective fragmentary view of an adsorptive powder injector used with the filter apparatus shown in FIGURE ll;

FIGURE 18 is a perspective view with portions broken away of a carbon cooling filter used with the filter apparatus shown in FIGURE l1;

FIGURE 19 is an elevational view of a third embodiment of the subject invention shown for exemplary purposes connected to an adsorptive powder injector and a conventional dry cleaning machine by piping (which for clarity is shown in simplified form with the omission of many of the valves and connectors);

FIGURE 20 is an enlarged fragmentary partial crosssectional view of a portion of the filter apparatus shown in FIGURE 19, showing a primary filter, a wiper, and a secondary filter above an outlet at the bottom of the tank;

FIGURE 21 is a perspective view of a portion of a turbulence suppressor shown in FIGURE 20, with a portion broken away in order to show the construction of turbulence suppressor in detail;

FIGURE 22 is an enlarged perspective view of the filter shown in FIGURE 19, showing in detail the primary and secondary filters and various valves and connections, with portions broken away to show the construction of the interior of the apparatus.

FIGURE 23 is a cross-sectional view of a portion of the primary filter and wiper shown in FIGURE 22;

FIGURE 24 is an elevational view of a portion of the primary filter and wiper shown in FIGURE 22, showing the Wiper (a brush) in engagement with the opposing surfaces of two filter elements, and further showing the brush in engagement with a stop to hold the brush against free rotation relative to the filter apparatus;

FIGURE 25 is an elevational view of a fourth embodiment of the subject invention, shown for exemplary purposes connected to an adsorptive powder injector and a conventional dry cleaning machine by piping (which for clarity is shown in simplified form, with the omission of many of the valves and connectors);

FIGURE 26 is a cross-sectional view of the filter apparatus shown in FIGURE 25, showing primary and secondary filter chambers with primary and secondary filters mounted therein;

FIGURE 27 is an enlarged fragmentary perspective view of the lower portion of the primary filter chamber and the secondary filter chamber shown in FIG-URE 26, showing a secondary filter and an auger mounted in the secondary filter chamber;

FIGURE 28 is an enlarged perspective view of the filter apparatus shown in FIGURE 25 showing in detail the various pipe sections and connections, with portions broken away to illustrate the construction of the interior of the apparatus;

FIGURE 29 is a cross-sectional end view of the secondary filter chamber shown in FIGURE 25, showing in detail the secondary filter and the auger mounted in the secondary filter chamber;

FIGURE 30 is an elevational view of a fifth embodiment of the subject invention, shown for exemplary purposes connected to an adsorptive powder injector and a conventional dry cleaning machine by piping (which for clarity is shown in simplified form, with the omission of many of the valves and connectors);

FIGURE 31 is an enlarged pictorial diagrammatic view of the filter apparatus shown in FIGURE 30, showing flow lines that illustrate the liquid liow paths to, from, and through the filter apparatus;

FIGURE 32 is an enlarged fragmentary perspective view of the filter apparatus shown in FIGURE 30, with portions broken away in order to show in the internal construction thereof;

FIGURE 33 is a cross-sectional elevational view of the apparatus Shown in FIGURE 30, showing a wiper in its furthermost extended position;

FIGURE 34 is an enlarged cross-sectional fragmentary view of the filter apparatus shown in FIGURE 30, showing the construction of primary and secondary filter elements;

FIGURE 35 is an enlarged fragmentary cross-sectional view of the filter apparatus shown in FIGURE 34, showing a portion of a primary filter element and a wiper in engagement therewith breaking-off chunks of filter cake;

FIGURE 36 is a fragmentary perspective view of the filter apparatus shown in FIGURE 30, with portions broken away, showing an alternative construction of primary filter elements in the form of plates;

FIGURE 37 is a fragmentary cross-sectional view of the filter apparatus shown in FIGURE 36, showing the interior construction of one of the plate elements;

FIGURE 38 is a perspective View of one of the plate elements shown in FIGURES 36 and 37; and

FIGURE 39 is a fragmentary perspective View of the filter apparatus shown in FIGURE 30, with parts broken away, showing an alternative form of primary filter elements wherein the filter elements are in a Vform.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment No. l-Dual-chamber filter With reference to the drawings, FIGURES l-lO show a first embodiment of the subject invention, comprising a dual-chamber filter apparatus, generally indicated by reference numeral 50. As shown in FIGURES l and 2, the filter apparatus 50 includes a frame or hollow rectanuglar casing 52 having legs 54 for supporting the casing and having upper and lower doors 56 and 58, respectively, in one end wall of the casing to provide access into the interior of the casing.

The interior of casing S2 is divided into an upper or primary filter chamber 60 and a lower or secondary filter chamber 62 by horizontal divider 64 which is attached to side walls 66 and 68 and to end Wall 70.

Upper and lower doors 56 and 58 are mounted on fiange 72, which extends around the periphery of an open end of casing 52. Flange 72 is provided with a sealing bar 74 (to separate the primary filter chamber 60 from the secondary filter chamber 62 when the upper door 56 is closed) and a cross bar 76 (to receive the lower edge of upper door 56 and the upper edge of lower door 58).

Primary filter chamber 60 is connected to a source of unclarified liquid, such as a dry cleaning machine (not shown), which pumps unclarified liquid containing solid and chemical impurities through pipe 78 into inlet header 80 mounted on end wall 70 and then through inlet apertures 82 formed in end wall 70 into the primary filter chamber 60. An air vent 83 is provided in the primary filter chamber to permit the expulsion of air from the chamber.

After the liquid fills primary chamber 60, the pump forcing the liquid into the filter chamber forces the liquid through a first mechanical filter or primary filter 84 rotatably mounted in the primary filter chamber 60, whereby solid particles are removed from the unclarified liquid. The liquid is then pumped out of the primary filter chamber through bearing seal housing 86 and into outlet pipe 88.

The construction of the primary filter 84 is shown in FIGURES l, 3, and 6. A hollow filter shaft 92 is rotatably mounted in a filter bracket 90 at one end of primary filter chamber 60 and in bearing seal housing 86 at the other end. As shown in FIGURE 6, filter shaft 92 has perforations through its walls and is closed at both ends.

A perforated filter tube 94 is mounted on shaft 92 for rotation therewith. The ends of tube 94 are fixed to plates 96, which are in turn fixed to filter shaft 92 to close the ends of the tube. The interior of tube 94 communicates with the interior of filter shaft 92 through the perforations in the shaft wall so that liquid may fiow through tube 94 into shaft 92.

As shown in FIGURES 3, 6, and 8, the filtering operation is accomplished by a series of hollow disc-shaped filter elements 98 mounted in coaxial alignment on filter tube 94 and separated by spacers 106, which cover the l() perforations in lter tube 94 between adjacent filter elements. Each filter element 98 includes a support structure or spacer 100 covered with a fine mesh screen 102. The support structure 100 is a fiat sheet of material folded in an accordian-like fold radiating outward from the center of the element and tapering to a point at the outer edge. The fine mesh screen 102 covering the support structure 100 has 325 by 325 openings per square inch (each opening being approximately 47 microns) so that all solid particles suspended in a liquid are retained on the screen when unclarified liquid is pumped through the filter. The outer periphery of each of the filter elements 98 has a metal rim 104 fixed thereon that slightly overlaps the screen and seals the outer periphery of the filter element.

In passing through the primary filter the unclarified liquid received in primary filter cham-ber 60 through inlet apertures 82 fiows from the high-pressure side of the primary filter through the fine mesh screen 102, along the pleats of the accordian-like support structure 100, through filter tube 94, and into filter shaft 92. The liquid then fiows along filter shaft 92 into bearing seal housing 86 and into outlet pipe 88. At this stage, all solid particles should be removed from the unclarified liquid and deposited as filtrate on the fine mesh screens 102 on the high-pressure side of primary filter.

After leaving the primary filter chamber through outlet pipe 88, the liquid then flows into chemical filter chamber 108 mounted on the top 71 of casing 52 and enters the chemical filter chamber through inlet pipes 110 and 112.

Chemical filter chamber 108, which is best seen in FIG- URE 5, includes a tubular outer casing 114 with a fixed head 116 sealingly mounted on the right end (FIGURE 5 orientation) and a removable head 118 sealingly mounted on the other end. A perforated interior tube 120 is mounted inside the chemical filter chamber 108 and extends through head 116. A closure 122 is threaded on the end of interior tube 120, and a stud 124 is threaded into an opening in closure 122. A Wing nut 126 is threaded on the stud in engagement with the closure. The stud extends through removable head 118 and engages a threaded handle 128 which holds the removable head 118 in position. An air vent 129 is provided in the chemical filter chamber to permit the expulsion of air from the chamber.

A chemical filter 130 mounted within chemical filter chamber 108 includes two identical filter sections 132 and 134 that are mounted in series on interior tube 120. Each section has an outer perforated tubular wall 136 and an inner perforated tubular wall 138 which are fastened together by end plates 140 and 142 to form a porous casing surrounding the perforated tube. Each casing is filled with granules of activated charcoal 144.

When liquid received from the primary filter chamber enters the chemical filter chamber through inlet pipes 110 and 112, the liquid fiows through the outer perforated tubular Wall 136 of the chemical filter, through the activated charcoal 144, through the inner perforated tubular wall 138, and into the interior of interior tube 120. As the liquid passes through the activated charcoal, chemical impurities dissolved in the liquid are adsorbed by the activated charcoal and retained in the chemical filter. The clarified liquid then fiows along interior tube 120 through fixed head 116 and to an appropriate receptacle for clean liquid (e.g., back to the dry cleaning machine).

As the filtering operation continues, filter cake removed from the unclarified liquid continues to build up on the high-pressure side of the primary lter, and this impedes the free fiow of unclarified liquids through the primary filter. Accordingly, provision is made in the subject apparatus for the intermittent removal of accumulated filter cake from the surface of the primary filter.

Wipers 146 are rotatably mounted on each spacer 106 separating the individual filter elements of the primary filter so that each wiper is in contact with the opposing Afaces of two adjacent filter elements. A drive means 148 is provided for rotating primary filter 84 relative to wipers 146. This relative motion between the wipers and :he primary filter elements causes the filter cake to be dis lodged from the surfaces of the filter elements into the inclarified liquid in primary filter chamber 60.

As shown in FIGURES 7 and 9, each wiper is slidably mounted on an arm 150 that is attached in a non-radial position to a ring 152, which is in turn rotatably mounted an spacer 106. Arm 150 is attached to ring 152 in the non-radial position shown (i.e., the filter rotates into an acute angle between the ring and the arm) so that the rotation of the filter relative to the wiper will automati- :ally urge the wiper to slide along the arm toward the axis of the filter and thereby ensure a firm contact between the wiper and the surface of the filter.

Each wiper includes a resilient U-shaped band 159 slidably mounted over each arm 150 (FIGURE 9 orientation) and brushes 156 fastened on the outside of the legs of the U-shaped band 154 by clips 158. A rod 160 is soldered to the U-shaped band 154 below the arm 150 to maintain the band in its U-shape. Each brush 156 has a woven backing 162 with nylon fibers 164 lodged therein and engages the surface of one filter element in the manner shown in FIGURE 6. An arm stop 166 is mounted on wall 66 of the primary filter chamber to prevent wipers 146 from rotating in a counterclockwise direction (the direction of rotation of the primary filter 84) so that the wipers Will remain stationary and brushes 156 will dislodge accumulated filter cake from the entire surface of the filter elements when drive means 148 rotates the primary filter.

It has been found that the speed at which the filter elements are rotated relative to the stationary wiper brushes is important to the efcient operation of the wiper 146. When the surface of the filter element is wiped at a speed greater than about 1000l inches per minute some of the filter cake is forced into and/ or through the fine mesh screen 102, thereby clogging the filter and reducing the effectiveness of the filtering operation. Moreover, this rapid wiping breaks the rest of the filter cake into particles that are so finely divided that they do not settle readily from the liquid surrounding the primary filter. If, on the other hand, a wiper speed of less than 1000 inches per minute is employed, preferably between about 200 and about 400` inches per minute, the wiping action forces the filter cake away from the filter surface and causes it to break off in large chunks that settle readily from the surrounding liquid. Accordingly, drive means 148 should be adjusted to provide the proper wiping speed in this apparatus.

Since particles dislodged from the primary filter 84 are placed in suspension in the liquid in the primary filter chamber 60, immediate resumption of the filtering opera* tion could cause these particles to be redeposited on the primary filter. Therefore, means are provided in the subject apparatus for removing dislodged filter cake from the primary filter chamber 60 by recirculating the liquid in the primary filter chamber through a secondary filter 182 in a secondary lter chamber 62 and returning the liquid directly back to the primary filter chamber 60 As shown in FIGURE 4, primary filter chamber 60 has a baffle 168 which extends most of the length of the entire chamber, leaving openings at the ends so that solvent may be drawn behind the bafiie from primary filter chamber 68. A conventional pump 170 mounted on wall 68 draws liquid from behind bafiie 168 through exhaust conduit 172 and delivers the liquid through delivery pipe 174 through one-way valve 176 and into header 178 mounted on end wall 70. The liquid then flows from header 178 through inlet aperture 180 into the secondary filter chamber 62.

Pump 17 0 then forces the liquid entraining the dislodged filter cake through a second mechanical filter or secondary filter 182 rotatably mounted in the secondary filter chamber in order to remove the dislodged filter from the liquid. After the liquid passes through secondary filter 182, it fiows into hollow filter shaft 184 (corresponding to filter shaft 92 of primary filter 84), along the shaft 184 out of secondary filter chamber 62, and into bearing seal housing 186 mounted on the outside of end wall 70. From the bearing seal housing 186, the liquid fiows into outlet pipe 188 and returns directly back to the primary filter chamber through header 190 on wall 66.

Header 190 has a plurality of spray nozzles 192 -mounted therein which spray the liquid returning to the primary filter chamber against the high-pressure sides of primary filter elements 98, and thereby aid wipers 146 in dislodging filter cake from the filter elements.

The construction of the secondary filter 182 is identical to the construction of the primary filter 84, and the secondary filter 182 is also connected to drive means 148 for rotation within the filter chamber. The only difference in the drive arrangement is that drive means 148 rotates the secondary filter in the opposite direction from which it rotates the primary filter. In this case, the secondary filter rotates in a clockwise direction and the primary filter rotates in a counterclockwise direction.

Wipers identical to the wipers 146 employed in cleaning primary filter 84 are also provided for cleaning the secondary filter 182. The only structural dissimilarities between the wipers are that the wipers for the secondary filter are adapted to operate with filter elements that are rotated in a clockwise direction, as shown in FIGURE 4. Stop 194 attached to wall 66 prevents the rotation of the wiper in a clockwise direction.

Filtrate dislodged from the secondary filter 182 by the rotation of the secondary filter in a clockwise direction relative to the wiper settles within secondary filter chamber 62 into a perforated collector basket 196 slidably mounted on supporting flanges 198 and 200 just above the bottom 69 of the secondary filter chamber. Supporting flanges 198 and 200 are mounted on side walls 66 and 68, respectively. Baffles 202 and 204, also mounted on wall 66 and 68, respectively, guide the settling dislodged filter cake into the collector basket.

The secondary filter chamber is provided with an air bleed valve 206 (shown in FIGURE l) and two liquid drain valves 208 and 210 which are attached to end wall and communicate with the interior of secondary filter chamber 62 (shown in FIGURE 3). The upper drain valve 208 is positioned just above collector basket 196 in the secondary filter chamber and is connected to a drain pipe 212 which leads to an appropriate storage tank for unclarified solvent (not shown). Another outlet from drain pipe 212 is a conduit 214 leading through shut off valve 216 to an inlet in chemical filter chamber 108. The lower drain valve 210 is placed at the bottom of the secondary filter chamber for draining solvent from the portion of the chamber containing the collector basket 196 so that the lower door 58 may be taken off and the collector basket may be removed for cleaning.

As stated above, the primary and secondary filters are rotatably driven in opposite directions by a single drive means 148. This drive means (shown in FIGURES 1 and 3) is constructed as follows. Hollow filter shaft 92 of the primary filter extends through bearing seal housing 86 and is connected to sprocket 218 through one-way clutch 220, which effects driving engagement between shaft 92 and sprocket 218 when sprocket 218 is rotated in a counterclockwise direction. Drive chain 222 connects sprocket 218 to a drive sprocket 224, which is mounted on an output shaft 226 of a reversible electric motor 228. Similarly, hollow filter shaft 184 of the secondary filter extends through its bearing seal housing 186 and is attached to a second sprocket 230 through one-way clutch 232 which effects driving engagement between the sprocket and shaft when the sprocket is rotated in a clockwise direction. A second drive chain 234 connects sprocket 230 with drive sprocket 224.

With the drive arrangement set up in this manner, when reversible electric motor 228 operates in a counterclock- 

